What statement is true of the configuration for this network?
A. The configuration that is shown provides inadequate outside address space for translation of the number of inside addresses that are supported. B. Because of the addressing on interface FastEthernet0/1, the Serial0/0 interface address will not support the NAT configuration as shown. C. The number 1 referred to in the ip nat inside source command references access-list number 1. D. ExternalRouter must be configured with static routes to networks 172.16.1.0/24 and 172.16.2.0/24.
Correct Answer: C
Explanation:
The “list 1″ refers to the access-list number 1.
Which statement describes the process of dynamically assigning IP addresses by the DHCP server?
A. Addresses are allocated after a negotiation between the server and the host to determine the length of the agreement. B. Addresses are permanently assigned so that the hosts uses the same address at all times. C. Addresses are assigned for a fixed period of time, at the end of the period, a new request for an address must be made. D. Addresses are leased to hosts, which periodically contact the DHCP server to renew the lease.
Correct Answer: D
Explanation: The DHCP lifecycle consists of the following:
Allocation: A client begins with no active lease, and hence, no DHCP-assigned address. It acquires a lease through a process of allocation.
Reallocation: If a client already has an address from an existing lease, then when it reboots or starts up after being shut down, it will contact the DHCP server that granted it the lease to confirm the lease and acquire operating parameters. This is sometimes called reallocation; it is similar to the full allocation process but shorter.
Normal Operation: Once a lease is active, the client functions normally, using its assigned IP address and other parameters during the “main part” of the lease. The client is said to be bound to the lease and the address.
Renewal: After a certain portion of the lease time has expired, the client will attempt to contact the server that initially granted the lease, to renew the lease so it can keep using its IP address.
Rebinding. If renewal with the original leasing server fails (because, for example, the server has been taken offline), then the client will try to rebind to any active DHCP server, trying to extend its current lease with any server that will allow it to do so.
Release: The client may decide at any time that it no longer wishes to use the IP address it was assigned, and may terminate the lease, releasing the IP address.
A. NAT facilitates end-to-end communication when IPsec is enabled. B. NAT eliminates the need to re-address all hosts that require external access. C. NAT conserves addresses through host MAC-level multiplexing. D. Dynamic NAT facilitates connections from the outside of the network. E. NAT accelerates the routing process because no modifications are made on the packets. F. NAT protects network security because private networks are not advertised.
Correct Answers: B, F
Explanation:
By not revealing the internal IP addresses, NAT adds some security to the inside network -> F is correct.
NAT has to modify the source IP addresses in the packets -> E is not correct.
Connection from the outside of the network through a “NAT” network is more difficult than a more network because IP addresses of inside hosts are hidden -> C is not correct.
In order for IPsec to work with NAT we need to allow additional protocols, including Internet Key Exchange (IKE), Encapsulating Security Payload (ESP) and Authentication Header (AH) -> more complex -> A is not correct.
By allocating specific public IP addresses to inside hosts, NAT eliminates the need to re-address the inside hosts -> B is correct.
NAT does conserve addresses but not through host MAC-level multiplexing. It conserves addresses by allowing many private IP addresses to use the same public IP address to go to the Internet -> C is not correct.
A. destination address and wildcard mask B. destination address and subnet mask C. source address and subnet mask D. source address and wildcard mask
Correct Answer: D
Explanation:
Standard ACL’s only examine the source IP address/mask to determine if a match is made. Extended ACL’s examine the source and destination address, as well as port information.
A network engineer wants to allow a temporary entry for a remote user with a specific username and password so that the user can access the entire network over the Internet. Which ACL can be used?
A. standard B. extended C. dynamic D. reflexive
Correct Answer: C
Explanation:
We can use a dynamic access list to authenticate a remote user with a specific username and password. The authentication process is done by the router or a central access server such as a TACACS+ or RADIUS server. The configuration of dynamic ACL can be read here: http://www.cisco.com/en/US/tech/tk583/tk822/technologies_tech_note09186a0080094524.shtml
How does a DHCP server dynamically assign IP addresses to hosts?
A. Addresses are permanently assigned so that the host uses the same address at all times. B. Addresses are assigned for a fixed period of time. At the end of the period, a new request for an address must be made, and another address is then assigned. C. Addresses are leased to hosts. A host will usually keep the same address by periodically contacting the DHCP server to renew the lease. D. Addresses are allocated after a negotiation between the server and the host to determine the length of the agreement.
Correct Answer: C
Explanation:
DHCP works in a client/server mode and operates like any other client/server relationship. When a PC connects to a DHCP server, the server assigns or leases an IP address to that PC. The PC connects to the network with that leased IP address until the lease expires. The host must contact the DHCP server periodically to extend the lease. This lease mechanism ensures that hosts that move or power off do not hold onto addresses that they do not need. The DHCP server returns these addresses to the address pool and reallocates them as necessary.
Which rule does the DHCP server use when there is an IP address conflict?
A. The address is removed from the pool until the conflict is resolved. B. The address remains in the pool until the conflict is resolved. C. Only the IP detected by Gratuitous ARP is removed from the pool. D. Only the IP detected by Ping is removed from the pool. E. The IP will be shown, even after the conflict is resolved.
Correct Answer: A
Explanation:
An address conflict occurs when two hosts use the same IP address. During address assignment, DHCP checks for conflicts using ping and gratuitous ARP. If a conflict is detected, the address is removed from the pool. The address will not be assigned until the administrator resolves the conflict.
The Bigtime router is unable to authenticate to the Littletime router. What is the cause of the problem?
A. The usernames are incorrectly configured on the two routers. B. The passwords do not match on the two routers. C. CHAP authentication cannot be used on a serial interface. D. The routers cannot be connected from interface S0/0 to interface S0/0. E. With CHAP authentication, one router must authenticate to another router. The routers cannot be configured to authenticate to each other.
Correct Answer: B
Explanation:
With CHAP authentication, the configured passwords must be identical on each router. Here, it is configured as little123 on one side and big123 on the other.
Which two tasks does the Dynamic Host Configuration Protocol perform? (Choose two.)
A. Set the IP gateway to be used by the network. B. Perform host discovery used DHCPDISCOVER message. C. Configure IP address parameters from DHCP server to a host. D. Provide an easy management of layer 3 devices. E. Monitor IP performance using the DHCP server. F. Assign and renew IP address from the default pool.
Correct Answers: C, F
Explanation:
The Dynamic Host Configuration Protocol (DHCP) is a network protocol used to configure devices that are connected to a network (known as hosts) so they can communicate on that network using the Internet Protocol (IP). It involves clients and a server operating in a client-server model. DHCP servers assigns IP addresses from a pool of addresses a and also assigns other parameters such as DNS and default gateways to hosts.
When a DHCP server is configured, which two IP addresses should never be assignable to hosts? (Choose two.)
A. network or subnetwork IP address B. broadcast address on the network C. IP address leased to the LAN D. IP address used by the interfaces E. manually assigned address to the clients F. designated IP address to the DHCP server
Correct Answers: A, B
Explanation:
Network or subnetwork IP address (for example 11.0.0.0/8 or 13.1.0.0/16) and broadcast address (for example 23.2.1.255/24) should never be assignable to hosts. When try to assign these addresses to hosts, you will receive an error message saying that they can’t be assignable.
